The present invention relates to a brake control apparatus used for a vehicle such as an automobile and more particularly, to a brake control apparatus for controlling a boost to the depressing force on a brake pedal. It further relates to a brake control apparatus for controlling brake forces of individual wheels such as in skid controls.
In conventionally operating brakes on wheels of an automobile, brake devices generally use oil pressure. In other words, the brake device has a master cylinder for generating oil pressure by means of the depression of a brake pedal. Oil pressure generated by the master cylinder is distributed from the master cylinder to a brake mechanism provided for each respective wheel. Brake pistons are respectively provided in the wheel cylinders, the pistons are driven in response to the hydraulic oil supplied from the master cylinder, and the wheels are respectively acted by the brake forces of brake pads driven by the pistons.
In this case, the operating force of the brake pedal is converted directly into oil pressure with which drives the piston in the wheel cylinder by means of the oil pressure. However, in order to effectively utilize the depressing force acted on the pedal, a booster is used. The booster mechanism is constructed such that it increases the oil pressure by a predetermined ratio over the oil pressure in the case that only the depressing force of the brake pedal is converted directly into oil pressure for the piston in the wheel cylinder.
With such booster mechanism, a more than sufficient brake force can be obtained for a good road stability. However, this booster mechanism is activated by a higher oil pressure so as to produce a stronger braking force. Thus, a hydraulic circuit from the master cylinder to the wheel cylinders requires high pressure lines. Further, in order to accrue brake forces of the same degree to the wheels during turning such as front and rear wheels or inner and outer wheels are under different conditions, a special load regulating means such as proportional valves is required.